热融湖影响下多年冻土退化的数值模拟

在柱坐标下,运用带相变的数值热传导模型,预测了千年尺度上热融湖对多年冻土退化的影响。预测结果表明,受热融湖的影响,湖底下部及周围多年冻土温度状态发生了较大变化。在湖深相同的情况下,湖底年平均温度越高,对多年冻土的热扰动越明显。当湖底年平均温度等于0℃时,湖底下部及周围多年冻土一般不会形成融化层,只可能引起地温升高;当湖底年平均温度大于0℃时,多年冻土不但温度升高,上限下移,而且可能形成融化层,最终导致多年冻土可能被融穿。湖底年平均温度越高,地温增加越快,融穿多年冻土的时间越短。在湖底年平均温度相同的情况下,水深差异对多年冻土退化的影响不明显。     

Removal of Aromatic Volatile Organic Compounds in the Sequencing Batch Reactor of Petroleum Refinery Wastewater Treatment Plant

This paper presents a field investigation of aromatic volatile organic compounds (AVOCs) emissions from a sequence batch reactor (SBR) with powdered activated carbon (PAC) to treat the wastewater in a large petroleum refinery plant. AVOC with high Henry's constant preferred to transfer from liquid‐phase into air‐phase so that might cause the emission and odor problem. During SBR operation, AVOC concentrations and distributions in wastewater, sludge and off‐gas were analyzed. The total AVOC removal from wastewater was >99% under the kinetic parameters of SBR operated. Batch experiments were carried out in the laboratory to obtain the adsorptive characteristic of AVOC onto PAC, but the results showed that bio‐degradation was the main removal mechanism (85%). Nevertheless, off‐gas emission (<1%) and AVOC in the sludge (<0.1%) remained a stable level. Oxidation/reduction potential (ORP) was correlated to the logarithm of the dissolved oxygen (DO) concentration in a linear relationship so that ORP profile could indirectly reflect the DO and biomass concentrations. Since the influent AVOC concentration was varied and difficultly to measure, ORP could be used as real‐time parameter for optimizing SBR operation. The results provided useful information for future evaluation of AVOC emissions from wastewater treatment plants.     

Historical Channel-Bed Elevation Change as a Result of Multiple Disturbances,Soldier Creek,Kansas

Historical information on stream stage/discharge relations from eight U.S. Geological Survey (USGS) streamflow-gaging stations was used to analyze channel-bed elevation change along Soldier Creek, a stream affected by multiple disturbances in northeast Kansas. The analysis provided information on the spatial (location, type, magnitude) and temporal (timing, duration, trend, rate) dimensions of channel change. Channel changes determined for Soldier Creek included extensive changes resulting from channelization and changes of relatively limited extent following a flood. The results were used to document channel changes, partly reconstruct historical channel conditions, infer the causes of channel change, and estimate the occurrence of future channel changes.     

Paleoenvironmental Changes in the Lake Baringo Basin,Kenya, East Africa Since AD 1650: Evidence from the Paleorecord∗

This article presents some of the findings of a multi-indicator investigation of the history of vegetational changes and land degradation in the Lake Baringo basin, Kenya, East Africa, during the Late Holocene. ¹⁴C- and ²¹⁰Pb-dated record of the lithostratigraphy is used to reconstruct the paleoenvironment in the region of the lake. The stratigraphic record from Lake Baringo reveals the presence of two abrupt dry episodes at ca. AD 1650 and AD 1720 in east Africa that led to drying up of the lake. The record also shows evidence of a third period of desiccation at ca. AD 1880, which resulted in lowering of the lake level and is corroborated by oral tradition from the area. This article shows the potential of how the paleoenvironmental record can be combined with the historical record to understand East Africa's paleoenvironment.     

藏北高寒草地退化现状、原因与恢复模式

藏北高寒草地系统生态脆弱且区位重要,草地退化和沙化的治理是目前学者们重点关注的领域之一。本文采用遥感解译、模型模拟、地面取样验证等相结合的方法,分析了藏北高寒草地生态系统退化的现状、趋势和原因,以实验为基础,总结了退化草地恢复的几种重要模式。数据分析表明：藏北羌塘高原轻度退化草地占62．0％,中度和重度退化草地占15．1％,1991年以来,退化面积快速增加,2000年以来重度退化面积增加趋势明显。藏北西部的草地轻度退化可能由气候暖千化所引起,而中部、东部的重度退化主要由超载过牧引起。总结出轻度退化草地的“封育”、中度退化草地的“施肥＋封育”、重度退化草地的“补播＋施肥＋封育”三种草地恢复模式。提出了退化草地恢复和保护的间接途径“南草北上”生态工程的战略构想。     

Future trends in transport and fate of diffuse contaminants in catchments,with special emphasis on stable isotope applications

A summary is provided of the first of a series of proposed Integrated Science Initiative workshops supported by the UNESCO International Hydrological Programme. The workshop brought together hydrologists, environmental chemists, microbiologists, stable isotope specialists and natural resource managers with the purpose of communicating new ideas on ways to assess microbial degradation processes and reactive transport at catchment scales. The focus was on diffuse contamination at catchment scales and the application of compound‐specific isotope analysis (CSIA) in the assessment of biological degradation processes of agrochemicals. Major outcomes were identifying the linkage between water residence time distribution and rates of contaminant degradation, identifying the need for better information on compound specific microbial degradation isotope fractionation factors and the potential of CSIA in identifying key degradative processes. In the natural resource management context, a framework was developed where CSIA techniques were identified as practically unique in their capacity to serve as distributed integrating indicators of process across a range of scales (micro to diffuse) of relevance to the problem of diffuse pollution assessment. Copyright © 2006 John Wiley & Sons, Ltd.     

SEFIDROOD RIVER SUB-WATERSHED-DAM-ESTUARY AND DEGRADATION MODEL： A HOLISTIC APPROACH IN IRAN

The major concern of this article is to address the shortcoming and outgoing effects of the human activities on the landscape patterns and their consequences in the Sefidrood River watershed in Iran. A flow of data includes three inputs; each of them belongs to one part of three zones of a fluvial system. The three parts of the Sefidrood River fluvial system include Zone 1, a sub-watershed as degradation modeling site, Zone 2, Sefidrood Dam asdam site, and Zone 3, 17kin away from the Sefidrood River path to the Caspian Sea as ending point site. The degra-dation model in the Zone 1 provides a suitable mean for decision support system to decrease the human impacts oneach small district. The maximum number for degradation coefficient belongs to the small district with the highest physiographic density, relatively cumulative activities, and a lower figure for the habitat vulnerability. The human degradation impact were not limited to the upstream. The investigation to the Sefidrood Dam and ending point of the Sefidrood River depicts that sedimentation continues as a significant visual impact in the Sefidrood Dam reservoir and the estuary.     

Use of the revised universal soil loss equation (RUSLE) for soil and nutrient loss estimation in long-used rainfed agricultural lands,North Ethiopia

This study was conducted to quantify agricultural land degradation in the Ruba Gered watershed, Ethiopia. The watershed was divided into 12 land mapping units (LMU) after superimposing maps of soil, slope, land use/cover, and elevation. Subsequently, cultivated land was delineated to assess degradation types and severity based on standard approaches. Sheet erosion was estimated using the revised universal soil loss equation. Composite soil samples were collected from each LMU to quantify key soil nutrients (OM, total nitrogen, available phosphorus, and available potassium) lost by sheet erosion. The annual average soil loss due to sheet erosion was estimated to be 17.4 t ha^?1 yr^?1, with average annual nutrient losses estimated as 246.5 kg ha^?1 organic matter, 12.4 kg ha^?1 total nitrogen, 0.1 kg ha^?1 available phosphorus, and 1.6 kg ha^?1 available potassium. The study revealed that substantial quantities of soil and nutrients are lost every year in the study area due to severe sheet erosion. This amount of nutrient loss severely degrades soil and reduces soil fertility.     

基于SEM-EDS及GC-MS技术研究有机氯分子结构对零价铜脱氯机制的影响

零价铜作为一种廉价金属很少应用于促进氯代有机物脱氯研究,其原因是零价铜的催化还原脱氯活性差,且反应机制复杂。本文采用机械球磨技术制备了Cu-Fe和Cu-Ni合金,研究零价铜在不同微观环境下对对氯苯酚(4-CP)的脱氯行为,旨在考察有机氯分子结构对零价铜脱氯机制的影响。应用扫描电镜-能谱(SEM-EDS)及色相色谱-质谱(GC-MS)分析发现,铜原子的微环境及有机氯分子结构均影响铜的脱氯机制。在Cu-Fe体系中,Cu遵循经典的催化加氢脱氯机制,4-CP的降解产物为苯酚;Cu-Ni体系的还原作用来源于零价铜,其中的镍金属并未起到催化加氢作用,Cu-Ni合金及单独零价铜对4-CP的降解产物是环己酮。零价铜对4-CP的降解率可达70%以上,而Cu-Fe体系的降解率仅为34%,两者对芳香族氯代物的降解效率差距显著。零价铜能够降解化学稳定性高的4-CP和苯酚,但不能降解化学稳定性相对较差的脂肪族氯代有机物(如一氯乙酸和二氯乙酸),因此认为零价铜脱氯机制并非传统的催化加氢机制,而是遵循直接电子传递还原机制,且有机氯分子的苯环结构是零价铜直接电子传递还原的诱因。     

甘肃张掖黑河流域中游湿地退化原因及治理对策

概述了甘肃张掖黑河流域中游湿地的特点及特殊生态地位,从自然和人为因素两个方面系统阐述了张掖黑河湿地的退化原因。从创新保护形势、科学修复、理顺管理体制、加快发展相关产业、促进湿地保护等方面提出了张掖黑河湿地保护管理对策及措施。